1. Field of the Invention
The present invention relates to a fuel cell vehicle. More specifically, the present invention relates to the fuel cell vehicle driven by electricity generated by a fuel cell.
2. Related Art
Recently, fuel cells have received focus as a new source of power for automobiles. A fuel cell vehicle with a fuel cell mounted thereto, for example, includes a fuel cell for generating electricity by a chemical reaction of reactant gas, a reactant gas supply device for supplying the reactant gas to the fuel cell via reactant gas lines, a motor for driving wheels by way of electricity generated by a fuel cell system, and a control device for control thereof.
The fuel cell, for example, has a stacked structure in which several tens to hundreds of cells are laminated. Each cell is configured by sandwiching a membrane electrode assembly (MEA) by a pair of plates. The membrane electrode assembly is configured by an anode and a cathode and a polymer electrolyte membrane which is arranged between the two electrodes.
As reactant gas, hydrogen gas and oxygen-containing air are supplied to the anode and cathode, respectively, of the fuel cell, thereby generating electricity by an electrochemical reaction.
In the fuel cell vehicle above, the motor is driven directly by electricity generated by the fuel cell, while storing electricity generated by the fuel cell into a power storage device such as a battery or a condenser, in order to drive the motor by using electricity of the power storage device when the fuel cell cannot generate electricity.
Incidentally, it would take time for such a fuel cell vehicle to start generating electricity from the fuel cell after ignition is turned ON. Due to this, the motor is driven by electricity from the power storage device until initialization of the fuel cell to generate electricity is complete, and after completion of the initialization of the fuel cell to generate electricity, the motor is driven by using electricity generated by the fuel cell.
For example, Japanese Unexamined Patent Application Publication No. 2005-73475 discloses a method for setting an upper limit value to an output of the power storage device, so that torque necessary to drive the motor by using electricity from the power storage device is ensured.
Nevertheless, since the fuel cell vehicle as described above controls only the output of power storage device, in a case where the electricity supply source is switched from the power storage device to the fuel cell, while an accelerator aggressively depressed, a sense of uneven torque may occur.
FIG. 5 is a timing chart of a fuel cell vehicle of the related art.
At time t0, the ignition is turned ON, battery initiation is prepared during time t0 to t1, and electricity can be supplied from the battery to the motor at time t1. Thus, after time t1, electricity that can be supplied to the motor is electricity supplied in the battery, which becomes constant at a predetermined value A.
Afterwards, at time t2, the driver presses the accelerator pedal, and the accelerator position is maintained at a maximum after time t2.
Then, during time t2 to t3, which is a startup time of the motor, rotation speed and power consumption of the motor increase and torque also increases rapidly. Afterwards, the power consumption of motor reaches the predetermined value A and becomes constant, the rotation speed of motor also increases to a certain extent, and the torque gradually decreases.
Continuing, the initialization of the fuel cell to generate electricity is complete, and at time t3, electricity generation of the fuel cell begins. Then, the electricity that can be supplied to the motor increases rapidly to a predetermined value B, and afterwards becomes constant.
Therefore, the rotation speed and the power consumption of the motor increase once again, and the torque also increases rapidly. Afterwards, the power consumption of the motor reaches the predetermined value B and becomes constant, the rotation speed of motor also increases to a certain extent, and the torque gradually decreases.
In the above way, at time t3, the torque, which gradually decreased until reaching time t3, increases rapidly, and a sense of uneven torque may occur when the electricity supply source switches from the power storage device to the fuel cell.